1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a backlight and a method of manufacturing a light guide plate, and more particularly, to a backlight having an all-in-one type light guide plate and a method of manufacturing the all-in-one type light guide plate.
2. Description of the Related Art
Typically, backlights are used to illuminate flat displays, for example, liquid crystal displays, and are mainly classified as direct light emitting type backlights or light guide plate type backlights depending on the positions of the light sources. Light guide plate type backlights may be also classified as flat type backlights or wedge type backlights.
In direct light emitting type backlights, a light source is installed close below a light exit surface, thereby enabling a surface light emission. Advantageously, direct light emitting type backlights include more light sources in comparison with light guide plate type backlights, thus increasing light brightness and widening the light exit surface. However, in direct light emitting type backlights, power consumption is higher because many light sources are used. Also, it is difficult to realize thin film direct light emitting type backlights because the shape of light sources is reflected, and thus light uniformity is severely reduced.
In light guide plate type backlights, a light guide plate is employed to guide light to a light exit surface. Light sources are disposed on a side surface of the light guide plate. The number of light sources is limited according to a length of a side surface of the light guide plate. Advantageously, thin film light guide plate type backlights can be realized easily. On the other hand, a process for making light brightness uniform on the entire light exit surface is complicated in comparison with direct light emitting type backlights.
Flat type backlights are used in monitors or when high-brightness is required. In flat type backlights, the light sources may be fixed to two or all four edges of the light guide plate. To increase light brightness when a plurality of light sources are used, an edge thickness of the light guide plate should be uniform.
Wedge type backlights are used in devices, such as notebook computers, in which it is difficult to use several light sources due to limited power resources. Only one surface constituting a light incident portion is widened and other surface is narrowed, to thereby reduce the weight of the backlight.
Light sources used in light guide plate type backlights may be line light-sources and point light-sources. A cold cathode fluorescent lamp (CCFL) may be used as a line light-source. In this case, electrodes at both ends of the CCFL are installed within a pipe. A light emitting diode (LED) may be used a point light-source. Advantageously, the CCFL emits strong white light having high-brightness and high-uniformity, and allows design enlargement. However, the CCFL is operated via a high frequency alternating current (AC) signal and at a narrow range of an operation temperature. Meanwhile, the performance of the LED is inferior to that of the CCFL in view of light brightness and uniformity. However, the LED has advantages of operating via a direct current (DC) signal and at a wide range of operation temperatures. In addition, LEDs have long lifespans and can be used to make a thin film direct light emitting type backlight.
FIG. 1 is a sectional view schematically illustrating a conventional side emitting type backlight.
Referring to FIG. 1, line light-sources 10 are installed at both sides 21 and 22 of a light guide plate 20. A light path converter 23 is formed on a lower surface of the light guide plate 20 to guide light incident from the line light-sources 10.
A plurality of prisms or prism-shaped structures 30 are formed on an upper side of the light guide plate 20 to diffuse the light coming out from an exit surface 24 into the upper side of the light guide plate 20. The prism-shaped structures 30 are fixed to the upper side of the light guide plate 20 by an adhesive layer 31.
The light incident from the line light-sources 10 into the light guide plate 20 is guided to the exit surface 24 of the light guide plate 20 by the light path converter 23. The light passes through an adhesive layer 31 and diffuses to the upper side of the light guide plate 20 through the prism-shaped structures 30.
Since the prism-shaped structures 30 are fixed to the upper side of the light guide plate 20 by the adhesive layer 31, the light incident into prism-shaped structures 30 must pass through the adhesive layer 31. Thus, the adhesive layer 31 affects the transmission of light. In particular, since the backlight performance depends on an adhering degree of the adhesive force, the adhesive layer 31 should be removed to increase the backlight performance.